title: Computer simulations of the phase separation in model membranes.
abstract: We used computer simulations to investigate the properties of model lipid membranes with coexisting phases. This is relevant for understanding lipid-lipid interactions underlying lateral organization in biological membranes. Molecular dynamics simulations with the MARTINI coarse-grained force field were employed to study lipid bilayers -40 nm in lateral dimension on a 20 micros time scale. The simulations retain near atomic-level detail and lipid chemical specificity, and allow formation of multiple domains of tens of nanometers in size. Using ternary lipid mixtures of saturated and unsaturated lipids and cholesterol, we reproduced the coexistence of the Lalpha/gel phases and the Lo/Ld phases. Phase transformation proceeded by either nucleation or spinodal decomposition. The properties of coexisting phases were characterized in detail, including partial lipid areas, composition, phase boundary and domain registry, based on Voronoi tessellation. We investigated variations of these properties with temperature and surface tension, and compared them to our recent simulations of lipid monolayers of the same size and composition. We found substantial overlap in bilayer and monolayer properties. Increasing the temperature in bilayers produced similar effects as increasing the surface tension in monolayers. This information can be used for interpreting experimental data on model membranes.
authors.affiliation: Department of Biological Sciences and Institute for Biocomplexity and Informatics, University of Calgary, 2500 University Dr NW, Calgary, AB, Canada T2N 1N4. s.baoukina@ucalgary.ca
authors.forename: Svetlana
authors.initials: S
authors.lastname: Baoukina
authors.forename: Eduardo
authors.initials: E
authors.lastname: Mendez-Villuendas
authors.forename: W F Drew
authors.initials: WF
authors.lastname: Bennett
authors.forename: D Peter
authors.initials: DP
authors.lastname: Tieleman
mesh_terms: D002462:Cell Membrane / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry; D013500:Surface Tension; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine